The 58-year-old socialist has not been seen in public nor heard from in almost a month following surgery in Cuba. The government says he is in a delicate condition and cannot attend Thursday's scheduled swearing-in for a new six-year term.

"Right now we cannot say when, how or where the president will be sworn in," Supreme Court Chief Judge Luisa Morales told a news conference.

"As president re-elect there is no interruption of performance of duties ... The inauguration can be carried out at a later date before the Supreme Court."

Both Chavez and his heir apparent, Vice President Nicolas Maduro, would remain in the roles after Jan. 10, she added in a judgment quashing opposition appeals for a caretaker president to be named.

Government leaders insist Chavez is fulfilling his duties as head of state, even though official medical bulletins said he suffered multiple complications after the surgery, including a severe pulmonary infection, and has had trouble breathing.

It was his fourth operation since being diagnosed with an undisclosed type of cancer in June 2011.

The government has called for a massive rally outside the presidential palace on Thursday, and allied presidents including Uruguay's Jose Mujica and Bolivia's Evo Morales have confirmed they will visit Venezuela that day despite Chavez's absence.

The president's resignation or death would upend politics in the oil-rich nation, where he is revered by poor supporters thankful for his social largesse.

His critics denounce him as an autocrat who has squandered billions of dollars from crude sales while dashing the independence of state institutions.